Proteins

Protein comes from a Greek word ‘Proteo’ meaning to take the first place’. They are complex organic compounds with nitrogen as an integral part. Proteins are made up of small units called amino acids. Each gram of protein provides 4 kcal of energy.

Functions

  • Essential for growth and repair of tissues.
  • Hemoglobin, an iron containing protein present in red blood cells, is responsible for carrying oxygen to various tissues.
  • Antibodies which are responsible for building up the body’s immune system are protein in nature.
  • Certain enzymes and hormones like insulin and thyroxine are also proteins.
  • Plasma proteins (present in blood) help in maintaining the fluid balance in the body.

Classification

Proteins can be classified as :

  • Complete proteins

o    They have all essential amino acids to supply the body’s needs.

o    These are of good quality.

  • Incomplete proteins

o    They are deficient in one or more essential amino acids.

o    Proteins obtained from these are of a lower quality than complete proteins

(If different foods from this group of protein are used in combination, the protein needs can be adequately met).

Sources

Complete proteins Incomplete proteins
These are obtained from animal sources like

  • Milk
  • Meat
  • Poultry
  • Fish
These are obtained from

  • Pulses or Legumes
  • Cereals

Guidelines

A normal individual needs 1 gm of protein per kg body weight per day. For a normal healthy person, the total intake of proteins should be 15 – 20% of the total calorie requirement. This requirement may go up during pregnancy and childhood. Certain disease conditions require modification in the protein intake.

Animal sources provide better quality protein but they are also rich in fats and excessive intake may lead to obesity and other cardiovascular disorders.

Though, pulses account for majority of the proteins obtained from vegetable sources, a single type of pulse may not contain all the essential amino acids required by the body. Therefore, individuals having a preference for vegetarian diet should always use a combination of pulses and cereals to meet the protein requirements.